The present invention relates to a sector opening/closing device using a stepping motor in a camera shutter.
Generally, a stepping motor incorporated in an opening/closing device of a camera is desired to have a high efficiency, consume less current and small in size because a battery is used as a power source. Besides, the stepping motor must be forward/reverse rotatable for effecting sector opening and closing operations, and so it requires at least two sets of coils and stators, thus resulting, according to the prior art, a construction in which each stator and iron core are separated, or a construction in which the stators are overlapped on a plane. Consequently, not only a larger number of components are required but also the support structures for the stator, etc. become more complicated, thus making it difficult to attain reduction in size and thickness. Further, the ordinary camera shutter portion is circular in shape and has a centrally formed lens aperture, so it is necessary that the sector opening/closing device is constituted in a doughnut-like space. But, conventional circular or square motor units are disadvantageous in point of space and thus have been inappropriate as sector opening/closing devices in compact cameras.
According to the present invention, therefore, there is provided a sector opening/closing device which has remedied the above-mentioned drawbacks.
More particularly, according to the present invention, in a sector opening/closing device having a plurality of sectors which form a lens aperture, a forward/reverse rotatable stepping motor and means for transmitting the operation of the stepping motor to the sectors, the stepping motor is composed of a radially 4-pole magnetized rotor, two U-shaped stators each having a pair of leg portion, each leg portion having a magnetic pole portion formed at the force end thereof in opposed relation to the outer periphery of the rotor, and coils for exciting the stators.